The present invention relates to a switching system with an improved message distributor, and in particular to a digital switching system with a message distributor for improved distribution of signaling messages, control messages for respective units of the switching system and of messages for the connection set up and release.
FIG. 1 shows a telecommunication system with a conventional switching system such as is implemented by the Siemens EWSD system, for example.
According to FIG. 1, such a conventional switching system comprises essentially of a line group 1 (LTG, line/trunk group) which implements, together with digital subscriber line units 2 (DLU, digital line unit), so-called connecting units for connecting subscriber terminals 3 and 4 which are to be switched. The subscriber terminals 3 and 4 can be connected either directly to the line group 1 here, or via the digital subscriber line units 2. The subscriber terminals 3 and 4 are, for example, analog or digital terminals, ISDN basic accesses, connections for smaller and medium-sized private switching systems etc. In order to switch or implement communication between the respective subscriber terminals 3 and 4, the switching system usually has a switching network 7 which preferably has a redundant switching network 7′ in order to avoid failures. In the switching network 7 and 7′ (SN), not only are the voice and data channels of the respective subscriber terminals 3 and 4 connected to one another but there is also communication between and control of respective units such as, for example, the line group 1 and the respective subscriber line unit 2.
In order to implement a signaling network which is superimposed on a user channel network, the conventional switching system according to FIG. 1 also has a signaling control unit 5 (CCNC, common channel signaling network control). The signaling network of the central signaling system No. 7 (CCS7, common channel signaling No. 7) is preferably controlled by the signaling control unit 5. The signaling messages transmitted in the signaling network do perform here the essential basis for the actual switching or coupling of the associated voice and data channels in a user channel network.
A switching control unit 6 and its redundant unit 6′ are used for centrally controlling the switching system. The switching control unit 6 or 6′ comprises essentially a message distributor 8 or distributor 8′ (MB, message buffer) which is not illustrated, for distributing the messages transmitted in the switching system. Such messages are, for example, signaling messages (CCS7 messages), control messages for controlling the digital subscriber line units 2, the line groups 1 and the switching network 7, 7′. The message buffer or distributor 8 is also connected for this purpose to a switching group control 10 (SGC) which carries out the actual actuation of the switching network 7, 7′. In addition, the messages distributed by the message distributor 8 are used for connecting setup and release and for software download for possible restarting of the system. The connection of the message distributor 8 to the switching network 7 is preferably implemented by means of HDLC interfaces each with a data rate of 64 kbit/s. The switching control unit 6 or 6′ not only has the message distributor 8 but also a co-ordination processor 9 (CP) for implementing actual routing and zoning by actuating the message distributor 8 and the signaling control unit 5. The connection of the signaling control unit 5 is preferably implemented here by means of an asynchronous interface ATM (asynchronous transfer mode). The co-ordination processor 9 has essentially a common memory 12 (CMY) and a switching processor 11 (CAP, call processor) which carry out the actual controlling of the switching processes.
A disadvantage in such a conventional switching system is, however, the extremely high loading of the co-ordination processor 9 which results, in particular, from the processing and passing on of signaling messages from the message distributor 8 to the signaling control unit 5. This results, particularly when implementing mobile phone systems in which mobile phone stations are connected to the respective line group 1, in a limitation to only 32 line groups because increased signaling occurs owing to the permanent cell transfer in mobile phone systems.